1. Field of the Invention
The present invention relates to a surface treated electrodeposited copper foil, wherein Rz and Ra on a surface which did not contact with a drum when producing an electrodeposited copper foil (hereinafter, referred to as an M surface) and asperity is a little on the surface, a production method thereof, and a circuit board using the surface treated copper foil.
2. Description of the Related Art
Attainting of a higher density has been pursued in an IC mounting board for driving a liquid crystal display as a display unit of a personal computer, cellular phone and PDA, etc. IC mounting boards are called chip-on films (COF) because the IC is directly mounted on the substrate film.
In chip-on film mounting, a position of the IC is detected by a light transmitting a film having a wiring pattern of a copper foil formed thereon. Visibility of the chip-on film (an ability of detecting the IC by a light) is largely affected by a surface roughness of the copper foil. A film part for a light to transmit is a part where an unnecessary copper foil part except for a copper circuit part is removed by etching, and asperity of a copper foil surface is transferred to the film surface when applying the copper foil to the film and remains. Accordingly, when the copper foil surface is rough, asperity on the film surface becomes large and an amount of a light capable of going straight decreases due to the asperity when the light transmits so as to deteriorate the visibility.
At present, as a countermeasure, a large number of electrodeposited copper foils use a surface which contacted with an electrolytic drum (an S surface, which is the other side of the M surface) as a surface to be put together with a film part in consideration of the visibility. However, since a drum surface is transferred to the S surface, the drum has to be changed when the drum surface becomes rough. Particularly, when using a drum for a long time, stripes arise on the copper foil surface (S surface) due to the drum roughness formed over time, and the stripes deteriorate the visibility and adversely affect flex resistance and elongation, so that maintenance costs of the drum increase, production costs of general products increase and the production capability declines.
Even if the Rz is small in quality, stripes of the drum surface are transferred to the copper foil surface, which therefore results in a trouble in etching, etc.
In a surface treated copper foil of the related arts, an S surface is used as a surface to be applied with a film and a surface treatment is performed on the S surface as a countermeasure. However, when the drum surface becomes rough, since the surface is transferred to the copper foil surface, stripe-shaped asperity is formed thereon and the asperity deteriorates the visibility. Accordingly, the drum has to be changed frequently to keep a smoothness degree on the drum surface and there are disadvantages that productivity of the copper foil declines and the costs increase.